U.S. patent application number 12/394997 was filed with the patent office on 2010-09-02 for method and apparatus for creating side information from data for use in interactive compression.
This patent application is currently assigned to SLIPSTREAM DATA INC.. Invention is credited to Salmaan AHMED, David SZE.
Application Number | 20100223398 12/394997 |
Document ID | / |
Family ID | 42667742 |
Filed Date | 2010-09-02 |
United States Patent
Application |
20100223398 |
Kind Code |
A1 |
AHMED; Salmaan ; et
al. |
September 2, 2010 |
METHOD AND APPARATUS FOR CREATING SIDE INFORMATION FROM DATA FOR
USE IN INTERACTIVE COMPRESSION
Abstract
A computer-implemented method of creating side information from
data for use in interactive compression includes identifying
constituents of the data, extracting at least one of the
constituents, and retaining the extracted constituents for use as a
unit of side information.
Inventors: |
AHMED; Salmaan; (Waterloo,
CA) ; SZE; David; (Waterloo, CA) |
Correspondence
Address: |
Borden Ladner Gervais LLP
1200 Waterfront Centre, 200 Burrad Street, P.O. Box 48600
Vancouver
BC
V7X 1T2
CA
|
Assignee: |
SLIPSTREAM DATA INC.
Waterloo
CA
|
Family ID: |
42667742 |
Appl. No.: |
12/394997 |
Filed: |
February 27, 2009 |
Current U.S.
Class: |
709/247 |
Current CPC
Class: |
H03M 7/30 20130101 |
Class at
Publication: |
709/247 |
International
Class: |
G06F 15/16 20060101
G06F015/16 |
Claims
1. A computer-implemented method of creating side information from
data for use in interactive compression, the method comprising:
identifying constituents of the data; extracting at least one of
the constituents; and retaining the extracted constituents for use
as a unit of side information.
2. The method according to claim 1, comprising storing the unit of
side information in a memory unit.
3. The method according to claim 1, comprising identifying a
media-type of the data prior to identifying constituents of the
data.
4. The method according to claim 1, comprising computing a unique
side information identifier for identifying the unit of side
information.
5. The method according to claim 4, comprising storing the unit of
side information in a memory unit in association with the unique
side information identifier.
6. The method according to claim 4, wherein the unique side
information identifier comprises a hash of the unit of side
information.
7. The method according to claim 6, wherein the unique side
information identifier comprises at least one of a length of the
unit of side information in bytes, a modification date and time of
the unit of side information, a version number, and a randomly
generated number.
8. The method according to claim 1, wherein identifying
constituents of the data comprises identifying displayable data and
remaining data.
9. The method according to claim 8, wherein extracting comprises
extracting the remaining data.
10. The method according to claim 1, comprising determining which
of said constituents of data to retain based on a number of child
nodes in a node-tree structure and based on length of text data for
rendering.
11. The method according to claim 10, wherein said determining
comprises determining, for each node in the node-tree structure, a
ratio of the number of child nodes to the length of text data for
rendering and wherein said extracting comprises extracting one of
constituents that are non-text data for rendering, constituents
that have a ratio greater than zero, and constituents that have
parent nodes that have a ratio greater than a predetermined
value.
12. The method according to claim 1, comprising sending the data to
another electronic device for creating a unit of side information
at the other electronic device for use in the interactive
compression.
13. The method according to claim 1, comprising sending the unit of
side information to another electronic device for use in the
interactive compression.
14. The method according to claim 1, comprising receiving the data
from a host server system for creating the unit of side
information.
15. The method according to claim 14, comprising receiving a unique
identifier for comparison to a computed unique identifier for
confirming that the data used for creating the unit of side
information is identical at the host system.
16. The method according to claim 1, comprising building grammar
and frequency counts from the extracted constituents.
17. A mobile device comprising: a housing; a display device exposed
by the housing; an input device; a memory unit within the housing;
and a processor within the housing and operably connected to the
display device, the input device and the memory unit for executing
a program stored in the memory unit to cause the electronic device
to create side information from data for use in interactive
compression by identifying constituents of the data, extracting at
least one of the constituents, and retaining the extracted
constituents for use as a unit of side information.
18. A computer program product comprising a computer-readable
medium having computer-readable code embodied therein for execution
by a processor of a mobile device for creating side information
from data for use in interactive compression by identifying
constituents of the data, extracting at least one of the
constituents, and retaining the extracted constituents for use as a
unit of side information.
Description
FIELD OF TECHNOLOGY
[0001] The present disclosure relates to a method of creating side
information for use in interactive compression.
BACKGROUND
[0002] In the field of data communication, data is typically
compressed so that the amount of information being transmitted is
reduced. Such data compression enables less traffic and therefore
faster transmission. Compression also reduces storage requirements,
which is especially important in communication to portable or
mobile communication devices with limited storage capacity. In
conventional communication between a server and a mobile
communication device, requested data, such as message data, a
website, or a digital file, is encoded, or compressed, by the
server, and then transmitted. A decoder at the mobile communication
device decodes the compressed data, and processes it appropriately,
for example, displaying it to the user.
[0003] Side information, or a priori information shared by both the
encoder and decoder, can be used in the compression and
decompression of transmitted data to improve compression
performance. The choice of side information influences the
compression ratio achieved by the compression. Significantly
improved compression can be achieved in systems, known as
interactive compression systems, that maintain shared caches of
side information. A class of such systems is grammar-based
compression of which Yang-Kieffer (YK) data compression is a
member. Side information that is correlated with the data being
compressed is utilized in YK compression to build a grammar and
collect frequency counts. This is used to achieve better
compression of the data being compressed.
[0004] It is important that both encoder and decoder use the same
side information in compression and decompression, thereby using
the same parameters (e.g. YK grammar and frequency counts) for
compression and decompression, respectively. While such compression
and decompression systems and techniques provide significant
compression of data, the compression and decompression occurs at
the expense of the use of limited resources on mobile devices.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] Embodiments of the present disclosure will now be described,
by way of example only, with reference to the attached Figures,
wherein:
[0006] FIG. 1 is a block diagram of an exemplary embodiment of a
mobile communication device;
[0007] FIG. 2 is a block diagram of an exemplary embodiment of a
communication subsystem component of the mobile device of FIG.
1;
[0008] FIG. 3 is an exemplary block diagram of a node of a wireless
network;
[0009] FIG. 4 is a block diagram illustrating components of a host
system in one exemplary configuration for use with the wireless
network of FIG. 3 and the mobile communication device of FIG.
1;
[0010] FIG. 5 is a schematic view of a mobile communication device
and a server;
[0011] FIG. 6 is a flowchart showing a method of interactive
compression for communication between the server and the mobile
communication device;
[0012] FIG. 7 is a flowchart a flowchart showing further steps in a
method of interactive compression for communication between the
server and the mobile device;
[0013] FIG. 8 shows a simplified example of data retrieved by a
server;
[0014] FIG. 9 shows the data of FIG. 8 after reducing the data in
accordance with an aspect of an embodiment;
[0015] FIG. 10 is a flowchart showing sub-steps in the method of
FIG. 6 according to one embodiment;
[0016] FIGS. 11A and 11B show a simplified example of data
retrieved by the server;
[0017] FIGS. 12 and 13 show hierarchical node tree structures
representing the data of FIGS. 11A and 11B;
[0018] FIG. 14 shows a hierarchical node tree structure of the data
of FIGS. 11A and 11B after reduction of the data in accordance with
the method of FIGS. 6, 7 and 10; and
[0019] FIG. 15 shows the data of FIGS. 11A and 11B after reduction
of the data in accordance with the method of FIGS. 6, 7 and 10.
DETAILED DESCRIPTION
[0020] Generally, described is a system and method for creating
side information from data for use in interactive compression
between parties, such as a server and a mobile communication
device. In an embodiment, the interactive data compression is
performed using a lossless data compression, such as that described
in U.S. Pat. No. 6,801,141 to Yang et al., which is hereby
incorporated by reference. This type of data compression, using
grammar transforms, or rules, is also known as Yang-Kieffer (YK)
data compression. In YK data compression, data is compressed into
an irreducible grammar form from which the original data may be
recovered. The grammar form of previously compressed data can be
used in compression of related data, particularly when dealing with
data having similar properties and/or content. This grammar form
can be used for subsequent compressions by storing parameters, such
as the actual grammar production rules and frequency counts, as
compression state information, and can result in much enhanced
compression, particularly in terms of increased speed of
compression and reduced use of processing resources.
[0021] It will be appreciated that for simplicity and clarity of
illustration, where considered appropriate, reference numerals may
be repeated among the figures to indicate corresponding or
analogous elements. In addition, numerous specific details are set
forth in order to provide a thorough understanding of the
embodiments described herein. However, it will be understood by
those of ordinary skill in the art that the embodiments described
herein may be practiced without these specific details. In other
instances, well-known methods, procedures and components have not
been described in detail so as not to obscure the embodiments
described herein. Also, the description is not to be considered as
limiting the scope of the embodiments described herein.
[0022] The embodiments described herein generally relate to a
mobile wireless communication device, hereafter referred to as a
mobile device. Examples of applicable communication devices include
pagers, cellular phones, cellular smart-phones, wireless
organizers, personal digital assistants, computers, laptops,
handheld wireless communication devices, wirelessly enabled
notebook computers and the like.
[0023] The mobile device is a two-way communication device with
advanced data communication capabilities including the capability
to communicate with other mobile devices or computer systems
through a network of transceiver stations. The mobile device may
also have the capability to allow voice communication. Depending on
the functionality provided by the mobile device, it may be referred
to as a data messaging device, a two-way pager, a cellular
telephone with data messaging capabilities, a wireless Internet
appliance, or a data communication device (with or without
telephony capabilities). To aid the reader in understanding the
structure of the mobile device and how it communicates with other
devices and host systems, reference will now be made to FIGS. 1
through 4.
[0024] Referring first to FIG. 1, shown therein is a block diagram
of an exemplary embodiment of a mobile device 100. The mobile
device 100 includes a number of components such as a main processor
102 that controls the overall operation of the mobile device 100.
Communication functions, including data and voice communications,
are performed through a communication subsystem 104. Data received
by the mobile device 100 can be decompressed and decrypted by
decoder 103, operating according to any suitable decompression
techniques (e.g. YK decompression, and other known techniques) and
encryption techniques (e.g. using an encryption techniques such as
Data Encryption Standard (DES), Triple DES, or Advanced Encryption
Standard (AES)). The communication subsystem 104 receives messages
from and sends messages to a wireless network 200. In this
exemplary embodiment of the mobile device 100, the communication
subsystem 104 is configured in accordance with the Global System
for Mobile Communication (GSM) and General Packet Radio Services
(GPRS) standards. The GSM/GPRS wireless network is used worldwide
and it is expected that these standards will be superseded
eventually by Enhanced Data GSM Environment (EDGE) and Universal
Mobile Telecommunications Service (UMTS). New standards are still
being defined, but it is believed that they will have similarities
to the network behavior described herein, and it will also be
understood by persons skilled in the art that the embodiments
described herein are intended to use any other suitable standards
that are developed in the future. The wireless link connecting the
communication subsystem 104 with the wireless network 200
represents one or more different Radio Frequency (RF) channels,
operating according to defined protocols specified for GSM/GPRS
communications. With newer network protocols, these channels are
capable of supporting both circuit switched voice communications
and packet switched data communications.
[0025] Although the wireless network 200 associated with mobile
device 100 is a GSM/GPRS wireless network in one exemplary
implementation, other wireless networks may also be associated with
the mobile device 100 in variant implementations. The different
types of wireless networks that may be employed include, for
example, data-centric wireless networks, voice-centric wireless
networks, and dual-mode networks that can support both voice and
data communications over the same physical base stations. Combined
dual-mode networks include, but are not limited to, Code Division
Multiple Access (CDMA) or CDMA2000 networks, GSM/GPRS networks (as
mentioned above), and future third-generation (3G) networks like
EDGE and UMTS. Some other examples of data-centric networks include
WiFi 802.11, Mobitex.TM. and DataTAC.TM. network communication
systems. Examples of other voice-centric data networks include
Personal Communication Systems (PCS) networks like GSM and Time
Division Multiple Access (TDMA) systems. The main processor 102
also interacts with additional subsystems such as a Random Access
Memory (RAM) 106, a flash memory 108, a display 110, an auxiliary
input/output (I/O) subsystem 112, a data port 114, a keyboard 116,
a speaker 118, a microphone 120, short-range communications 122 and
other device subsystems 124.
[0026] Some of the subsystems of the mobile device 100 perform
communication-related functions, whereas other subsystems may
provide "resident" or on-device functions. By way of example, the
display 110 and the keyboard 116 may be used for both
communication-related functions, such as entering a text message
for transmission over the network 200, and device-resident
functions such as a calculator or task list.
[0027] The mobile device 100 can send and receive communication
signals over the wireless network 200 after required network
registration or activation procedures have been completed. Network
access is associated with a subscriber or user of the mobile device
100. To identify a subscriber, the mobile device 100 requires a
SIM/RUIM card 126 (i.e. Subscriber Identity Module or a Removable
User Identity Module) to be inserted into a SIM/RUIM interface 128
in order to communicate with a network. The SIM card or RUIM 126 is
one type of a conventional "smart card" that can be used to
identify a subscriber of the mobile device 100 and to personalize
the mobile device 100, among other things. Without the SIM card
126, the mobile device 100 is not fully operational for
communication with the wireless network 200. By inserting the SIM
card/RUIM 126 into the SIM/RUIM interface 128, a subscriber can
access all subscribed services. Services may include: web browsing
and messaging such as e-mail, voice mail, Short Message Service
(SMS), and Multimedia Messaging Services (MMS). More advanced
services may include: point of sale, field service and sales force
automation. The SIM card/RUIM 126 includes a processor and memory
for storing information. Once the SIM card/RUIM 126 is inserted
into the SIM/RUIM interface 128, it is coupled to the main
processor 102. In order to identify the subscriber, the SIM
card/RUIM 126 can include some user parameters such as an
International Mobile Subscriber Identity (IMSI). An advantage of
using the SIM card/RUIM 126 is that a subscriber is not necessarily
bound by any single physical mobile device. The SIM card/RUIM 126
may store additional subscriber information for a mobile device as
well, including datebook (or calendar) information and recent call
information. Alternatively, user identification information can
also be programmed into the flash memory 108.
[0028] The mobile device 100 is a battery-powered device and
includes a battery interface 132 for receiving one or more
rechargeable batteries 130. In at least some embodiments, the
battery 130 can be a smart battery with an embedded microprocessor.
The battery interface 132 is coupled to a regulator (not shown),
which assists the battery 130 in providing power V+ to the mobile
device 100. Although current technology makes use of a battery,
future technologies such as micro fuel cells may provide the power
to the mobile device 100.
[0029] The mobile device 100 also includes an operating system 134
and software components 136 to 146 which are described in more
detail below. The operating system 134 and the software components
136 to 146 that are executed by the main processor 102 are
typically stored in a persistent store such as the flash memory
108, which may alternatively be a read-only memory (ROM) or similar
storage element (not shown). Those skilled in the art will
appreciate that portions of the operating system 134 and the
software components 136 to 146, such as specific device
applications, or parts thereof, may be temporarily loaded into a
volatile store such as the RAM 106. Other software components can
also be included, as is well known to those skilled in the art.
[0030] The subset of software applications 136 that control basic
device operations, including data and voice communication
applications, will normally be installed on the mobile device 100
during its manufacture. Other software applications include a
message application 138 that can be any suitable software program
that allows a user of the mobile device 100 to send and receive
electronic messages. Various alternatives exist for the message
application 138 as is well known to those skilled in the art.
Messages that have been sent or received by the user are typically
stored in the flash memory 108 of the mobile device 100 or some
other suitable storage element in the mobile device 100. In at
least some embodiments, some of the sent and received messages may
be stored remotely from the device 100 such as in a data store of
an associated host system that the mobile device 100 communicates
with.
[0031] The software applications can further include a device state
module 140, a Personal Information Manager (PIM) 142, and other
suitable modules (not shown). The device state module 140 provides
persistence, i.e. the device state module 140 ensures that
important device data is stored in persistent memory, such as the
flash memory 108, so that the data is not lost when the mobile
device 100 is turned off or loses power.
[0032] The PIM 142 includes functionality for organizing and
managing data items of interest to the user, such as, but not
limited to, e-mail, contacts, calendar events, voice mails,
appointments, and task items. A PIM application has the ability to
send and receive data items via the wireless network 200. PIM data
items may be seamlessly integrated, synchronized, and updated via
the wireless network 200 with the mobile device subscriber's
corresponding data items stored and/or associated with a host
computer system. This functionality creates a mirrored host
computer on the mobile device 100 with respect to such items. This
can be particularly advantageous when the host computer system is
the mobile device subscriber's office computer system.
[0033] The mobile device 100 also includes a connect module 144,
and an information technology (IT) policy module 146. The connect
module 144 implements the communication protocols that are required
for the mobile device 100 to communicate with the wireless
infrastructure and any host system, such as an enterprise system,
that the mobile device 100 is authorized to interface with.
Examples of a wireless infrastructure and an enterprise system are
given in FIGS. 3 and 4, which are described in more detail
below.
[0034] The connect module 144 includes a set of APIs that can be
integrated with the mobile device 100 to allow the mobile device
100 to use any number of services associated with the enterprise
system. The connect module 144 allows the mobile device 100 to
establish an end-to-end secure, authenticated communication pipe
with the host system. A subset of applications for which access is
provided by the connect module 144 can be used to pass IT policy
commands from the host system to the mobile device 100. This can be
done in a wireless or wired manner. These instructions can then be
passed to the IT policy module 146 to modify the configuration of
the device 100. Alternatively, in some cases, the IT policy update
can also be done over a wired connection.
[0035] Other types of software applications can also be installed
on the mobile device 100. These software applications can be third
party applications, which are added after the manufacture of the
mobile device 100. Examples of third party applications include
games, calculators, utilities, etc.
[0036] The additional applications can be loaded onto the mobile
device 100 through at least one of the wireless network 200, the
auxiliary I/O subsystem 112, the data port 114, the short-range
communications subsystem 122, or any other suitable device
subsystem 124. This flexibility in application installation
increases the functionality of the mobile device 100 and may
provide enhanced on-device functions, communication-related
functions, or both. For example, secure communication applications
may enable electronic commerce functions and other such financial
transactions to be performed using the mobile device 100.
[0037] The data port 114 enables a subscriber to set preferences
through an external device or software application and extends the
capabilities of the mobile device 100 by providing for information
or software downloads to the mobile device 100 other than through a
wireless communication network. The alternate download path may,
for example, be used to load an encryption key onto the mobile
device 100 through a direct and thus reliable and trusted
connection to provide secure device communication.
[0038] The data port 114 can be any suitable port that enables data
communication between the mobile device 100 and another computing
device. The data port 114 can be a serial or a parallel port. In
some instances, the data port 114 can be a USB port that includes
data lines for data transfer and a supply line that can provide a
charging current to charge the battery 130 of the mobile device
100.
[0039] The short-range communications subsystem 122 provides for
communication between the mobile device 100 and different systems
or devices, without the use of the wireless network 200. For
example, the subsystem 122 may include an infrared device and
associated circuits and components for short-range communication.
Examples of short-range communication standards include standards
developed by the Infrared Data Association (IrDA), Bluetooth, and
the 802.11 family of standards developed by IEEE.
[0040] In use, a received signal such as a text message, an e-mail
message, or web page download will be processed by the
communication subsystem 104 and input to the main processor 102.
The main processor 102 will then process the received signal for
output to the display 110 or alternatively to the auxiliary I/O
subsystem 112. A subscriber may also compose data items, such as
e-mail messages, for example, using the keyboard 116 in conjunction
with the display 110 and possibly the auxiliary I/O subsystem 112.
The auxiliary subsystem 112 may include devices such as: a touch
screen, mouse, track ball, infrared fingerprint detector, or a
roller wheel with dynamic button pressing capability. The keyboard
116 is preferably an alphanumeric keyboard and/or telephone-type
keypad. However, other types of keyboards may also be used. A
composed item may be transmitted over the wireless network 200
through the communication subsystem 104.
[0041] For voice communications, the overall operation of the
mobile device 100 is substantially similar, except that the
received signals are output to the speaker 118, and signals for
transmission are generated by the microphone 120. Alternative voice
or audio I/O subsystems, such as a voice message recording
subsystem, can also be implemented on the mobile device 100.
Although voice or audio signal output is accomplished primarily
through the speaker 118, the display 110 can also be used to
provide additional information such as the identity of a calling
party, duration of a voice call, or other voice call related
information.
[0042] Referring now to FIG. 2, an exemplary block diagram of the
communication subsystem component 104 is shown. The communication
subsystem 104 includes a receiver 150, a transmitter 152, as well
as associated components such as one or more embedded or internal
antenna elements 154 and 156, Local Oscillators (LOs) 158, and a
processing module such as a Digital Signal Processor (DSP) 160. The
particular design of the communication subsystem 104 is dependent
upon the communication network 200 with which the mobile device 100
is intended to operate. Thus, it should be understood that the
design illustrated in FIG. 2 serves only as one example.
[0043] Signals received by the antenna 154 through the wireless
network 200 are input to the receiver 150, which may perform such
common receiver functions as signal amplification, frequency down
conversion, filtering, channel selection, and analog-to-digital
(A/D) conversion. A/D conversion of a received signal allows more
complex communication functions such as demodulation and decoding
to be performed in the DSP 160. In a similar manner, signals to be
transmitted are processed, including modulation and encoding, by
the DSP 160. These DSP-processed signals are input to the
transmitter 152 for digital-to-analog (D/A) conversion, frequency
up conversion, filtering, amplification and transmission over the
wireless network 200 via the antenna 156. The DSP 160 not only
processes communication signals, but also provides for receiver and
transmitter control. For example, the gains applied to
communication signals in the receiver 150 and the transmitter 152
may be adaptively controlled through automatic gain control
algorithms implemented in the DSP 160.
[0044] The wireless link between the mobile device 100 and the
wireless network 200 can contain one or more different channels,
typically different RF channels, and associated protocols used
between the mobile device 100 and the wireless network 200. An RF
channel is a limited resource that should be conserved, typically
due to limits in overall bandwidth and limited battery power of the
mobile device 100.
[0045] When the mobile device 100 is fully operational, the
transmitter 152 is typically keyed or turned on only when it is
transmitting to the wireless network 200 and is otherwise turned
off to conserve resources. Similarly, the receiver 150 is
periodically turned off to conserve power until it is needed to
receive signals or information (if at all) during designated time
periods.
[0046] Referring now to FIG. 3, a block diagram of an exemplary
implementation of a node 202 of the wireless network 200 is shown.
In practice, the wireless network 200 comprises one or more nodes
202. In conjunction with the connect module 144, the mobile device
100 can communicate with the node 202 within the wireless network
200. In the exemplary implementation of FIG. 3, the node 202 is
configured in accordance with General Packet Radio Service (GPRS)
and Global Systems for Mobile (GSM) technologies. The node 202
includes a base station controller (BSC) 204 with an associated
tower station 206, a Packet Control Unit (PCU) 208 added for GPRS
support in GSM, a Mobile Switching Center (MSC) 210, a Home
Location Register (HLR) 212, a Visitor Location Registry (VLR) 214,
a Serving GPRS Support Node (SGSN) 216, a Gateway GPRS Support Node
(GGSN) 218, and a Dynamic Host Configuration Protocol (DHCP) 220.
This list of components is not meant to be an exhaustive list of
the components of every node 202 within a GSM/GPRS network, but
rather a list of components that are commonly used in
communications through the network 200.
[0047] In a GSM network, the MSC 210 is coupled to the BSC 204 and
to a landline network, such as a Public Switched Telephone Network
(PSTN) 222 to satisfy circuit switched requirements. The connection
through the PCU 208, the SGSN 216 and the GGSN 218 to a public or
private network (Internet) 224 (also referred to herein generally
as a shared network infrastructure) represents the data path for
GPRS capable mobile devices. In a GSM network extended with GPRS
capabilities, the BSC 204 also contains the Packet Control Unit
(PCU) 208 that connects to the SGSN 216 to control segmentation,
radio channel allocation and to satisfy packet switched
requirements. To track the location of the mobile device 100 and
availability for both circuit switched and packet switched
management, the HLR 212 is shared between the MSC 210 and the SGSN
216. Access to the VLR 214 is controlled by the MSC 210.
[0048] The station 206 is a fixed transceiver station and together
with the BSC 204 form fixed transceiver equipment. The fixed
transceiver equipment provides wireless network coverage for a
particular coverage area commonly referred to as a "cell". The
fixed transceiver equipment transmits communication signals to and
receives communication signals from mobile devices within its cell
via the station 206. The fixed transceiver equipment normally
performs such functions as modulation and possibly encoding and/or
encryption of signals to be transmitted to the mobile device 100 in
accordance with particular, usually predetermined, communication
protocols and parameters, under control of its controller. The
fixed transceiver equipment similarly demodulates and possibly
decodes and decrypts, if necessary, any communication signals
received from the mobile device 100 within its cell. Communication
protocols and parameters may vary between different nodes. For
example, one node may employ a different modulation scheme and
operate at different frequencies than other nodes.
[0049] For all mobile devices 100 registered with a specific
network, permanent configuration data such as a user profile is
stored in the HLR 212. The HLR 212 also contains location
information for each registered mobile device and can be queried to
determine the current location of a mobile device. The MSC 210 is
responsible for a group of location areas and stores the data of
the mobile devices currently in its area of responsibility in the
VLR 214. Further, the VLR 214 also contains information on mobile
devices that are visiting other networks. The information in the
VLR 214 includes part of the permanent mobile device data
transmitted from the HLR 212 to the VLR 214 for faster access. By
moving additional information from a remote HLR 212 node to the VLR
214, the amount of traffic between these nodes can be reduced so
that voice and data services can be provided with faster response
times and at the same time requiring less use of computing
resources.
[0050] The SGSN 216 and the GGSN 218 are elements added for GPRS
support; namely packet switched data support, within GSM. The SGSN
216 and the MSC 210 have similar responsibilities within the
wireless network 200 by keeping track of the location of each
mobile device 100. The SGSN 216 also performs security functions
and access control for data traffic on the wireless network 200.
The GGSN 218 provides internetworking connections with external
packet switched networks and connects to one or more SGSN's 216 via
an Internet Protocol (IP) backbone network operated within the
network 200. During normal operations, a given mobile device 100
must perform a "GPRS Attach" to acquire an IP address and to access
data services. This requirement is not present in circuit switched
voice channels as Integrated Services Digital Network (ISDN)
addresses are used for routing incoming and outgoing calls.
Currently, all GPRS capable networks use private, dynamically
assigned IP addresses, thus requiring the DHCP server 220 connected
to the GGSN 218. There are many mechanisms for dynamic IP
assignment, including using a combination of a Remote
Authentication Dial-In User Service (RADIUS) server and a DHCP
server. Once the GPRS Attach is complete, a logical connection is
established from a mobile device 100, through the PCU 208, and the
SGSN 216 to an Access Point Node (APN) within the GGSN 218. The APN
represents a logical end of an IP tunnel that can either access
direct Internet compatible services or private network connections.
The APN also represents a security mechanism for the network 200,
insofar as each mobile device 100 must be assigned to one or more
APNs and mobile devices 100 cannot exchange data without first
performing a GPRS Attach to an APN that it has been authorized to
use. The APN may be considered to be similar to an Internet domain
name such as "myconnection.wireless.com".
[0051] Once the GPRS Attach operation is complete, a tunnel is
created and all traffic is exchanged within standard IP packets
using any protocol that can be supported in IP packets. This
includes tunneling methods such as IP over IP as in the case with
some IPSecurity (IPsec) connections used with Virtual Private
Networks (VPN). These tunnels are also referred to as Packet Data
Protocol (PDP) Contexts and there are a limited number of these
available in the network 200. To maximize use of the PDP Contexts,
the network 200 will run an idle timer for each PDP Context to
determine if there is a lack of activity. When a mobile device 100
is not using its PDP Context, the PDP Context can be de-allocated
and the IP address returned to the IP address pool managed by the
DHCP server 220.
[0052] Referring now to FIG. 4, shown therein is a block diagram
illustrating components of an exemplary configuration of a host
system 250 that the mobile device 100 can communicate with in
conjunction with the connect module 144. The host system 250 will
typically be a corporate enterprise or other local area network
(LAN), but may also be a home office computer or some other private
system, for example, in variant implementations. In this example
shown in FIG. 4, the host system 250 is depicted as a LAN of an
organization to which a user of the mobile device 100 belongs.
Typically, a plurality of mobile devices can communicate wirelessly
with the host system 250 through one or more nodes 202 of the
wireless network 200.
[0053] The host system 250 comprises a number of network components
connected to each other by a network 260. For instance, a user's
desktop computer 262a with an accompanying cradle 264 for the
user's mobile device 100 is situated on a LAN connection. The
cradle 264 for the mobile device 100 can be coupled to the computer
262a by a serial or a Universal Serial Bus (USB) connection, for
example. Other user computers 262b-262n are also situated on the
network 260, and each may or may not be equipped with an
accompanying cradle 264. The cradle 264 facilitates the loading of
information (e.g. PIM data, private symmetric encryption keys to
facilitate secure communications) from the user computer 262a to
the mobile device 100, and may be particularly useful for bulk
information updates often performed in initializing the mobile
device 100 for use. The information downloaded to the mobile device
100 may include certificates used in the exchange of messages.
[0054] It will be understood by persons skilled in the art that the
user computers 262a-262n will typically also be connected to other
peripheral devices, such as printers, etc. which are not explicitly
shown in FIG. 4. Furthermore, only a subset of network components
of the host system 250 are shown in FIG. 4 for ease of exposition,
and it will be understood by persons skilled in the art that the
host system 250 will comprise additional components that are not
explicitly shown in FIG. 4 for this exemplary configuration. More
generally, the host system 250 may represent a smaller part of a
larger network (not shown) of the organization, and may comprise
different components and/or be arranged in different topologies
than that shown in the exemplary embodiment of FIG. 4.
[0055] To facilitate the operation of the mobile device 100 and the
wireless communication of messages and message-related data between
the mobile device 100 and components of the host system 250, a
number of wireless communication support components 270 can be
provided. In some implementations, the wireless communication
support components 270 can include a message management server 272,
a mobile data server (MDS) 274, a web server, such as Hypertext
Transfer Protocol (HTTP) server 275, a contact server 276, and a
device manager module 278. HTTP servers can also be located outside
the enterprise system, as indicated by the HTTP server 275 attached
to the network 224. The device manager module 278 includes an IT
Policy editor 280 and an IT user property editor 282, as well as
other software components for allowing an IT administrator to
configure the mobile devices 100. In an alternative embodiment,
there may be one editor that provides the functionality of both the
IT policy editor 280 and the IT user property editor 282. The
support components 270 also include a data store 284, and an IT
policy server 286. The IT policy server 286 includes a processor
288, a network interface 290 and a memory unit 292. The processor
288 controls the operation of the IT policy server 286 and executes
functions related to the standardized IT policy as described below.
The network interface 290 allows the IT policy server 286 to
communicate with the various components of the host system 250 and
the mobile devices 100. The memory unit 292 can store functions
used in implementing the IT policy as well as related data. Those
skilled in the art know how to implement these various components.
Other components may also be included as is well known to those
skilled in the art. Further, in some implementations, the data
store 284 can be part of any one of the servers.
[0056] In this exemplary embodiment, the mobile device 100
communicates with the host system 250 through node 202 of the
wireless network 200 and a shared network infrastructure 224 such
as a service provider network or the public Internet. Access to the
host system 250 may be provided through one or more routers (not
shown), and computing devices of the host system 250 may operate
from behind a firewall or proxy server 266. The proxy server 266
provides a secure node and a wireless internet gateway for the host
system 250. The proxy server 266 intelligently routes data to the
correct destination server within the host system 250.
[0057] In some implementations, the host system 250 can include a
wireless VPN router (not shown) to facilitate data exchange between
the host system 250 and the mobile device 100. The wireless VPN
router allows a VPN connection to be established directly through a
specific wireless network to the mobile device 100. The wireless
VPN router can be used with the Internet Protocol (IP) Version 6
(IPV6) and IP-based wireless networks. This protocol can provide
enough IP addresses so that each mobile device has a dedicated IP
address, making it possible to push information to a mobile device
at any time. An advantage of using a wireless VPN router is that it
can be an off-the-shelf VPN component, and does not require a
separate wireless gateway and separate wireless infrastructure. A
VPN connection can preferably be a Transmission Control Protocol
(TCP)/IP or User Datagram Protocol (UDP)/IP connection for
delivering the messages directly to the mobile device 100 in this
alternative implementation.
[0058] Messages intended for a user of the mobile device 100 are
initially received by a message server 268 of the host system 250.
Such messages may originate from any number of sources. For
instance, a message may have been sent by a sender from the
computer 262b within the host system 250, from a different mobile
device (not shown) connected to the wireless network 200 or a
different wireless network, or from a different computing device,
or other device capable of sending messages, via the shared network
infrastructure 224, possibly through an application service
provider (ASP) or Internet service provider (ISP), for example.
[0059] The message server 268 typically acts as the primary
interface for the exchange of messages, particularly e-mail
messages, within the organization and over the shared network
infrastructure 224. Each user in the organization that has been set
up to send and receive messages is typically associated with a user
account managed by the message server 268. Some exemplary
implementations of the message server 268 include a Microsoft
Exchange.TM. server, a Lotus Domino.TM.server, a Novell
Groupwise.TM.server, or another suitable mail server installed in a
corporate environment. In some implementations, the host system 250
may comprise multiple message servers 268. The message server 268
may also be adapted to provide additional functions beyond message
management, including the management of data associated with
calendars and task lists, for example.
[0060] When messages are received by the message server 268, they
are typically stored in a data store associated with the message
server 268. In at least some embodiments, the data store may be a
separate hardware unit, such as data store 284, that the message
server 268 communicates with. Messages can be subsequently
retrieved and delivered to users by accessing the message server
268. For instance, an e-mail client application operating on a
user's computer 262a may request the e-mail messages associated
with that user's account stored on the data store associated with
the message server 268. These messages are then retrieved from the
data store and stored locally on the computer 262a. The data store
associated with the message server 268 can store copies of each
message that is locally stored on the mobile device 100.
Alternatively, the data store associated with the message server
268 can store all of the messages for the user of the mobile device
100 and only a smaller number of messages can be stored on the
mobile device 100 to conserve memory. For instance, the most recent
messages (i.e. those received in the past two to three months for
example) can be stored on the mobile device 100.
[0061] When operating the mobile device 100, the user may wish to
have e-mail messages retrieved for delivery to the mobile device
100. The message application 138 operating on the mobile device 100
may also request messages associated with the user's account from
the message server 268. The message application 138 may be
configured (either by the user or by an administrator, possibly in
accordance with an organization's IT policy) to make this request
at the direction of the user, at some pre-defined time interval, or
upon the occurrence of some pre-defined event. In some
implementations, the mobile device 100 is assigned its own e-mail
address, and messages addressed specifically to the mobile device
100 are automatically redirected to the mobile device 100 as they
are received by the message server 268.
[0062] The message management server 272 can be used to
specifically provide support for the management of messages, such
as e-mail messages, that are to be handled by mobile devices.
Generally, while messages are still stored on the message server
268, the message management server 272 can be used to control when,
if, and how messages are sent to the mobile device 100. The message
management server 272 also facilitates the handling of messages
composed on the mobile device 100, which are sent to the message
server 268 for subsequent delivery.
[0063] For example, the message management server 272 may monitor
the user's "mailbox" (e.g. the message store associated with the
user's account on the message server 268) for new e-mail messages,
and apply user-definable filters to new messages to determine if
and how the messages are relayed to the user's mobile device 100.
The message management server 272 may also, through an encoder 273,
compress messages, using any suitable compression technology (e.g.
YK compression, and other known techniques) and encrypt messages
(e.g. using an encryption technique such as Data Encryption
Standard (DES), Triple DES, or Advanced Encryption Standard (AES)),
and push them to the mobile device 100 via the shared network
infrastructure 224 and the wireless network 200. The message
management server 272 may also receive messages composed on the
mobile device 100 (e.g. encrypted using Triple DES), decrypt and
decompress the composed messages, re-format the composed messages
if desired so that they will appear to have originated from the
user's computer 262a, and re-route the composed messages to the
message server 268 for delivery.
[0064] Certain properties or restrictions associated with messages
that are to be sent from and/or received by the mobile device 100
can be defined (e.g. by an administrator in accordance with IT
policy) and enforced by the message management server 272. These
may include whether the mobile device 100 may receive encrypted
and/or signed messages, minimum encryption key sizes, whether
outgoing messages must be encrypted and/or signed, and whether
copies of all secure messages sent from the mobile device 100 are
to be sent to a pre-defined copy address, for example.
[0065] The message management server 272 may also be adapted to
provide other control functions, such as only pushing certain
message information or pre-defined portions (e.g. "blocks") of a
message stored on the message server 268 to the mobile device 100.
For example, in some cases, when a message is initially retrieved
by the mobile device 100 from the message server 268, the message
management server 272 may push only the first part of a message to
the mobile device 100, with the part being of a pre-defined size
(e.g. 2 KB). The user can then request that more of the message be
delivered in similar-sized blocks by the message management server
272 to the mobile device 100, possibly up to a maximum pre-defined
message size. Accordingly, the message management server 272
facilitates better control over the type of data and the amount of
data that is communicated to the mobile device 100, and can help to
minimize potential waste of bandwidth or other resources.
[0066] The MDS 274 encompasses any other server that stores
information that is relevant to the corporation. The mobile data
server 274 may include, but is not limited to, databases, online
data document repositories, customer relationship management (CRM)
systems, or enterprise resource planning (ERP) applications. The
MDS 274 can also connect to the Internet or other public network,
through HTTP server 275 or other suitable web server such as an
File Transfer Protocol (FTP) server, to retrieve HTTP webpages and
other data. Requests for webpages are typically routed through MDS
274 and then to HTTP server 275, through suitable firewalls and
other protective mechanisms. The web server then retrieves the
webpage over the Internet, and returns it to MDS 274. As described
above in relation to message management server 272, MDS 274 is
typically provided, or associated, with an encoder 277 that permits
retrieved data, such as retrieved webpages, to be compressed, using
any suitable compression technology (e.g. YK compression, and other
known techniques), and encrypted (e.g. using an encryption
technique such as DES, Triple DES, or AES), and then pushed to the
mobile device 100 via the shared network infrastructure 224 and the
wireless network 200.
[0067] The contact server 276 can provide information for a list of
contacts for the user in a similar fashion as the address book on
the mobile device 100. Accordingly, for a given contact, the
contact server 276 can include the name, phone number, work address
and e-mail address of the contact, among other information. The
contact server 276 can also provide a global address list that
contains the contact information for all of the contacts associated
with the host system 250.
[0068] It will be understood by persons skilled in the art that the
message management server 272, the MDS 274, the HTTP server 275,
the contact server 276, the device manager module 278, the data
store 284 and the IT policy server 286 do not need to be
implemented on separate physical servers within the host system
250. For example, some or all of the functions associated with the
message management server 272 may be integrated with the message
server 268, or some other server in the host system 250.
Alternatively, the host system 250 may comprise multiple message
management servers 272, particularly in variant implementations
where a large number of mobile devices need to be supported.
[0069] The device manager module 278 provides an IT administrator
with a graphical user interface with which the IT administrator
interacts to configure various settings for the mobile devices 100.
As mentioned, the IT administrator can use IT policy rules to
define behaviors of certain applications on the mobile device 100
that are permitted such as phone, web browser or Instant Messenger
use. The IT policy rules can also be used to set specific values
for configuration settings that an organization requires on the
mobile devices 100 such as auto signature text, WLAN/VoIP/VPN
configuration, security requirements (e.g. encryption algorithms,
password rules, etc.), specifying themes or applications that are
allowed to run on the mobile device 100, and the like.
[0070] Referring to FIG. 5, a schematic view of the mobile device
100 and a server, such as MDS 274, the message management server
272 or any other server involved in the transfer of information or
data to and from the mobile device 100 is shown. The mobile device
100 and the server can be seen as communicating parties for a
method of interactive compression.
[0071] The mobile device 100 includes a main processor 102, a
decoder 103, and a device side information database 314, which can
also be described as a cache, store, or repository. The device side
information database 314 stores units of side information 316. Side
information is information that is used to describe parameters
associated with data such as emails or web pages. Side information
is a priori information that is known to both the encoder and
decoder. It can be correlated with the data that is being
compressed, such as emails in the same thread or web pages from the
same site and is used to improve compression. In order to be able
to decode data compressed using side information, the decoder uses
the same side information used by the encoder. This side
information can be represented in different forms including but not
limited to compression state information 318. The compression state
information 318 includes parameters, such as grammar, which
consists of production rules and/or frequency statistics, of
previously completed compressions. As previously noted, the
compression state information from previously completed
compressions can improve compression of subsequent data having
similar properties and/or content. The server includes a processor
320, and has access to an encoder, such as encoder 277, and a
server side information database 324. The encoder 277 and the
server side information database 324 can be integral with the
server, or separate therefrom. The server side information database
324 generally contains side information, including compression
state information, associated with the mobile device 100. The
server is connected to the network 200 so that it may retrieve data
from other servers connected to the network, such as HTTP server
275, as is described in more detail below. The side information
stored in the respective side information databases 314 and 324 can
be organized in any suitable manner for searching and retrieval by
the device side decoder 103 and the server side encoder 277,
respectively.
[0072] Interactive compression according to the present disclosure
can be generally understood by reference to an exemplary
transmission to the mobile device 100, such as an HTTP webpage.
[0073] FIG. 6 is a flowchart of a method of interactive compression
for communication between the server and the mobile device 100. The
mobile device 100 identifies data to request, such as a webpage
identified by a Uniform Resource Locator (URL), and a request for
the identified data is transmitted from the mobile device 100 to
the server along with an indication that the mobile device 100 is
YK-enabled (step 400). The request therefore includes an indication
that the decoder 103 can accept content compressed using side
information. In the example of the HTTP webpage, a request header
is sent from the decoder 103 to the encoder 277, including the
requested URL, and the indication that the decoder 103 can accept
content compressed using side information. An exemplary request
header can include, for example:
[0074] GET/HTTP/1.1
[0075] Host: www.example.com
[0076] Accept-Encoding: gzip, side-info-impl
[0077] Connection: keep-alive
In this example, the "Accept-Encoding" field in the request header
indicates to the encoder that the decoder is able to accept content
compressed using side information. The mobile device 100 then
awaits receipt of the requested data transmitted from the
server.
[0078] The request sent from the mobile device 100 is received at
the server (step 402) and the server identifies the requested data
and begins retrieving the identified requested data (step 404). The
requested data can be located within the server or can be
accessible through a remote server, such as HTTP server 275, over
the network 200. Continuing with the above example of requesting an
HTTP webpage, the requested data is identified using the URL
provided in the request header and the server begins retrieving the
requested data from the webpage.
[0079] The server then determines the media-type as well as the
data source, for determining if an appropriate unit of side
information is available for compressing and decompressing the
requested data (step 406). Thus, the identity of media-type of the
data, such as HTML, XML, RTF, etc., as well as the data source is
determined and the server searches the server side information
database 324 to determine if a suitable unit of side information,
based on the media-type and data source, is associated with the
mobile device 100 (step 408). The server thereby determines if a
suitable unit of side information has been previously stored for
the mobile device 100 for the identified media-type and data source
and if not, the data is compressed without the use of side
information (step 410). According to the present embodiment, the
first time data of a particular media-type and data source is
requested, no side information exists in association with the
mobile device 100 and therefore the data retrieved is compressed
without the benefit of the use of side information.
[0080] The server then transmits a response to the mobile device
100. The compression method used is identified in the response sent
to the mobile device 100 (step 412) and the requested data is
transmitted. Rather than waiting for all of the requested data to
be retrieved, the server can begin streaming the response to the
mobile device 100 shortly after beginning retrieval of the
requested data (when the requested data begins to arrive). It will
be appreciated that there may be a minimum amount that the server
retrieves before the side information is selected and before
starting to transmit the data. For example, the server may require
receipt of an entire HTTP header prior to determining if suitable
side information is stored for the mobile device 100.
Alternatively, the server may wait to receive some minimum amount
of data for inspection to determine the media-type of the response
such as plain text, HTML, XML, CSS, JavaScript, an image format . .
. etc. It will now be appreciated that it is not necessary that all
the data be retrieved at the server prior to beginning compression
and transmission of data.
[0081] Data for retaining is then determined (step 414). In the
present embodiment, constituents of the data are determined to
identify the displayable data and the remaining data, including
structure and formatting information for rendering data, based on
the media-type of the data. The remaining data (data for retaining)
including the structure and formatting is then extracted for use as
the unit of side information for compressing data of similar
media-type and data source in response to future requests (step
416). In one example, HTML data can be requested by the mobile
device 100 and retrieved by the server. An exemplary HTML fragment
is shown below including displayable data and the remaining data
including the structure and formatting.
[0082] <HTML>
[0083] <BODY>
[0084] Exemplary displayable HTML data
[0085] </BODY>
[0086] </HTML>
[0087] In the above example the "Exemplary displayable HTML data"
is identified as displayable data at step 414 and the remaining
constituents include the structure and formatting as referred to
above. The structure and formatting are extracted for use as the
side information. Thus, the remaining constituents are extracted
from the exemplary HTML fragment shown above, resulting in the
exemplary constituents shown below.
[0088] <HTML>
[0089] <BODY>
[0090] </BODY>
[0091] </HTML>
Any CSS-style (Cascading Style Sheets) descriptions or JavaScript
contained in the document is also preserved for use in the side
information.
[0092] Next, a unique identifier is computed for the extracted data
including the structure and formatting, referred to now as the unit
of side information (step 418). The unique identifier is employed
to ensure that the decoder 103 of the mobile device 100 uses the
same unit of side information for decompression as the encoder 277
uses for compression on the server side. The unique identifier can
be any identifier that uniquely identifies the unit of side
information, such as a hash of the bytes of side information along
with other information such as the length of the side information
in bytes. Thus, the unique identifier is computed by performing a
hashing operation such as MD5, MD4, SHA-1, CRC-32, CRC-16 or any
other suitable hashing operation that provides a good hash
distribution and the length of the side information, in bytes, is
included. To ensure the unique identifier is truly unique, other
information can be incorporated into the unique identifier. For
example, a portion or form of the URL can be included in the unique
identifier for an HTTP based application. Other information can
also be included to form the unique identifier such as a
modification date and time of the unit of side information, a
version number and/or a randomly generated number.
[0093] The unit of side information is cached (step 420), storing
the unit of side information in the server side information
database 324 in association with the unique identifier for use in
compressing data of the same media-type and data source in response
to future requests from the mobile device 100. The server side
information database 314 can store more than one unit of side
information as units of side information apply to like data formats
and data sources.
[0094] The response including the identity of the compression
method used is received at the mobile device 100 (step 422) and it
is determined that no side information was used to compress the
data. Thus, the decoder 103 decompresses the received data and
renders the data on the display 110 (step 424). The mobile device
100 determines the media-type of the requested data (step 426).
Thus, the identity of the media-type of the data, such as HTML,
XML, RTF, etc., is determined and the data for retaining is
determined based on the media-type of the data (step 428). In the
present embodiment, constituents of the data are determined to
identify the displayable data and the remaining data, including the
structure and formatting for rendering, based on the identity of
the media-type of the data. The remaining data (data for retaining)
including the structure and formatting is extracted from the data
for use as the unit of side information for decompressing data of
similar media-type received in response to future requests (step
430).
[0095] Next, the unique identifier is computed for the extracted
data, referred to now as the unit of side information (step 432).
As indicated above, the unique identifier is employed to ensure
that the decoder 103 of the mobile device 100 uses the same unit of
side information for decompression as the encoder 277 uses for
compression on the server side. The unique identifier can be any
identifier that uniquely identifies the unit of side information,
such as a hash of the bytes of side information along with other
information such as the length of the side information in bytes.
Thus, the unique identifier is computed using the identical
operation at the mobile device 100 as that at the server, described
above with reference to step 418. Thus, the same hashing operation
such as MD5, MD4, SHA-1, CRC-32, CRC-16 or any other suitable
hashing operation is performed at the mobile device 100 as that
performed by the server and the same information such as the length
of the side information, in bytes, is included to ensure the unique
identifier is truly unique.
[0096] The reduced data is used to build the grammar and collect
frequency counts for compression of data (step 433) and the side
information including the grammar and frequency counts is
compressed using YK compression without the use of any side
information (step 434). It will be appreciated that compression
using YK compression may be optional. In the present embodiment,
the reduced data including the grammar and frequency counts is
compressed to reduce the data for storage on the mobile device.
Thus, further units of side information can be stored in the same
storage space.
[0097] The compressed data is cached (step 435), storing the unit
of side information including the grammar and frequency counts in
the device side information database 314 in association with the
unique identifier for use in decompressing data of similar
media-type received in response to future requests. The device side
information database 314 can store more than one unit of side
information as units of side information only apply to like data
formats. Thus, the unit of side information is reduced by removing
displayable data at both the mobile device 100 and the server.
[0098] Returning to step 408, the server searches the server side
information database 324 to determine if a suitable unit of side
information, based on media-type and data source, is associated
with the mobile device 100. The server thereby determines if a
suitable unit of side information has been previously stored for
the mobile device 100 for the media-type and the data source and if
so, the unit of side information is retrieved along with the unique
identifier, as shown in FIG. 7 (step 436). According to the present
embodiment, the first time data of a particular media-type and data
source is requested, no side information exists in association with
the mobile device 100 and therefore the data retrieved is
compressed without the benefit of the use of side information. The
second time data of a particular media-type and data source is
requested, the server and the mobile device 100 have a unit of side
information stored in association with a unique identifier in their
respective side information databases 324, 314.
[0099] After retrieving the unit side information based on the
media-type and data source, along with the unique identifier of the
side information, the server builds the grammar and collects
frequency counts and compresses the data using the side
information, grammar and frequency counts (step 438). The server
then transmits a response to the mobile device 100. The compression
method used is identified in the response sent to the mobile device
100 along with the identifier of the unit of side information and
the requested data is transmitted (step 440). As described above,
rather than waiting for all of the requested data to be retrieved,
the server can begin streaming the response to the mobile device
100 shortly after beginning retrieval of the requested data (when
the requested data begins to arrive). It will be appreciated that
there may be a minimum amount that the server retrieves before the
side information is selected and before starting to transmit the
data. For example, the server may require receipt of the entire
HTTP header prior to selection of the side information for
compression. It will now be appreciated that it is not necessary
that all the data be retrieved at the server prior to retrieving
the unit of side information and prior to beginning compression and
transmission. After beginning transmission of the identifier of the
unit of side information and the requested data, the process
returns to step 414 and, as described above with reference to FIG.
6, and the data for retaining is determined (step 428). In the
present embodiment, the constituents of the data retrieved are then
determined including the displayable content and the remaining data
including structure and formatting based on the identity of the
media-type of the data. The process proceeds through the remaining
steps 416 to 420 and the new unit of side information created from
the data is cached, storing the unit of side information in the
server side information database 324 in association with the unique
identifier for use in compressing data of the same media-type and
data source in response to future requests from the mobile device
100. Many units of side information can therefore be stored in the
server side information database 324 and the side information cache
size can be managed using any suitable technique.
[0100] It will be appreciated that if the data sent to the mobile
device 100 at step 440 is identical to data previously sent to the
mobile device 100, the unit of side information cached at step 420
will be the same as a previously cached unit of side information
and will have the same side information identifier. Thus, only a
single cache entry is stored in the server side information
database 324 for the data as the unit of side information
overwrites the previous unit of side information stored in
association with the side information identifier. It will also be
appreciated that data such as an HTML page that differs in
displayable data from data previously sent to the mobile device 100
may result in identical side information and therefore an identical
side information identifier after reducing the data. Again, only a
single cache entry is stored in the server side information
database 324 in association with the side information
identifier.
[0101] In the embodiment described above with reference to FIG. 6,
data is sent to the mobile device in response to receipt of a
request for data. It will be appreciated that data such as email
data can be sent to the mobile device 100 in a "push" operation,
and therefore, a unit of side information is selected and the data
is compressed and sent automatically without receipt of a request
for data at the server.
[0102] Continuing still with the above example of requesting an
HTTP webpage, an HTTP response header is sent from the encoder 277
to the decoder 103. The HTTP response header indicates the
compression method used in compressing the data at the encoder 277
as well as the unique identifier of the unit of side information
used. The following HTTP response header is provided for exemplary
purposes only.
[0103] HTTP/1.1 200 OK
[0104] Connection: close
[0105] Content-Type: text/html
[0106] Content-Encoding: side-info-impl
[0107] X-Side-Info-Identifier: 0xE323FA21
In this example, the unit of side information used is identified
using the unique identifier 0xE323FA21.
[0108] The response including the unique identifier of the unit of
side information is received at the mobile device 100 (step 442)
and the unit of side information resident on the mobile device 100,
in the side information database 314, is identified using the
unique identifier and the decoder 103 loads the unit of side
information for use in decompressing the received data (step 444).
The received data is then decompressed using the unit of side
information and rendered on the display 110 (step 446).
[0109] After all the data is received and decompressed, the process
returns to step 426 and, as described above with reference to FIG.
6, the mobile device 100 identifies the media-type and source of
the requested data. The process proceeds through the remaining
steps 428 to 435 and the new unit of side information created from
the data including the grammar and frequency counts is compressed
and cached, storing the unit of side information in the device side
information database 314 in association with the unique identifier
for use in decompressing data of the same media-type and data
source. Many units of side information can therefore be stored in
the device side information database 314 and the side information
cache size can be managed using any suitable technique.
[0110] It will be appreciated that if the data received at the
mobile device 100 at step 442 is identical to data previously
received at the mobile device 100, the unit of side information
cached at step 435 will be the same as a previously cached unit of
side information and will have the same side information
identifier. Thus, only a single cache entry is stored in the device
side information database 314 for the data as the unit of side
information overwrites the previous unit of side information stored
in association with the side information identifier. It will also
be appreciated that data such as an HTML page that differs in
content from data previously received at the mobile device 100 may
result in identical side information and therefore an identical
side information identifier after reducing the data. Again, only a
single cache entry is stored in the device side information
database 314 in association with the side information
identifier.
[0111] As described, the unit of side information is identified at
the mobile device 100 and loaded into the decoder based on the
unique identifier. If no matching unique identifier is found in the
device side information database 314, a request for side
information can be sent to the server, for example. A matching
unique identifier and associated unit of side information may not
be found if, for example, an error occurred during reducing the
side information by removing the content. Alternatively, when
messages are pushed to the mobile device, data may be re-ordered
over the network and therefore a pushed mail message may reference
a unit of side information that has not yet been received at the
mobile device 100. It is possible for several messages to be
received in a queue at the mobile device 100 prior to receipt of
the unit of side information for decompressing the messages, for
example. Further, certain conditions may result in the loss of a
unit or units of side information. For example, removal of the
battery 130, wiping of memory or certain other conditions may
result in loss of units of side information stored in the device
side information database 314.
[0112] Continued reference is made to FIGS. 6 and 7 to describe
another embodiment. In the present embodiment, the mobile device
100 determines the unit of side information for use in compression
and decompression, rather than the server. The mobile device 100
identifies data to request, such as a webpage identified by a
Uniform Resource Locator (URL), and the request for the identified
data is transmitted from the mobile device 100 to the server along
with an indication that the mobile device 100 is YK-enabled and a
unique identifier of the unit of side information selected by the
mobile device 100 based on the data being requested (step 400). The
request therefore includes an indication that the decoder 103 can
accept content compressed using side information and an indication
of the unit of side information to use for compression. In the
example of the HTTP webpage, a request header is sent from the
decoder 103 to the encoder 277, including the requested URL, the
indication that the decoder 103 can accept content compressed using
side information, and the unique identifier of the unit of side
information. An exemplary request header according to the present
embodiment can include, for example:
[0113] Host: www.example.com
[0114] Accept-Encoding: gzip, side-info-impl
[0115] X-Use-SideInfo: 0x12345678
In this example, the "Accept-Encoding" field in the request header
indicates to the encoder that the decoder is able to accept content
compressed using side information and the X-Use-SideInfo:0x12345678
indicates the unit of side information to use for compression. The
mobile device 100 then awaits receipt of the requested data
transmitted from the server.
[0116] The request sent from the mobile device 100 is received at
the server (step 402) and the server identifies the requested data
and begins retrieving the identified requested data (step 404). The
server then determines the media-type as well as the data source
(step 406) and determines if the unit of side information is
available for compressing the requested data (step 408). In the
present example, the server determines if the unit of side
information, as identified in the request from the mobile device
100, is available. Thus, the server searches the server side
information database 324 for the unit of side information,
identified by the unique identifier of the unit of side
information.
[0117] If the side information identified by the mobile device 100
in the request is not resident in the server side information
database 324, the data is compressed without the use of side
information (step 410). The server then transmits a response to the
mobile device 100. The compression method used is identified in the
response and an indication that no side information was used is
provided (step 412). The requested data is transmitted. As
described above, the server can begin streaming the response to the
mobile device 100 shortly after beginning retrieval of the
requested data (when the requested data begins to arrive). There
may be a minimum amount that the server retrieves before starting
to compress and then transmit the data.
[0118] The data for retaining is then determined (step 414). In the
present embodiment, the constituents of the data are determined to
identify the displayable data as well as the remaining data
including the structure and formatting of the data based on the
identity of the media-type of the data. The remaining data
including the structure and formatting is then extracted (step
416). Next, a unique identifier is computed for the remaining data,
referred to now as the unit of side information (step 418). The
unique identifier is employed to ensure that the decoder 103 of the
mobile device 100 uses the same unit of side information for
decompression as the encoder 277 uses for compression on the server
side. As previously described, the unique identifier can be any
identifier that uniquely identifies the unit of side information,
such as a hash of the bytes of side information along with other
information such as the length of the side information in bytes.
The unit of side information is cached (step 420), storing the unit
of side information in the server side information database 324 in
association with the unique identifier for use in compressing data
of the same media-type and data source in response to future
requests from the mobile device 100. The server side information
database 314 can store more than one unit of side information as
units of side information apply to like data formats and data
sources.
[0119] The response including the identity of the compression
method used is received at the mobile device 100 (step 422) and it
is determined that no side information was used to compress the
data. Thus, the decoder 103 decompresses the received data and
renders the data on the display 110 (step 424). The mobile device
100 identifies the media-type (step 426). The data for retaining is
then determined (step 428). In the present embodiment, the
constituents of the data are determined to identify the displayable
data and the remaining data including the structure and formatting
for rendering based on the identity of the media-type of the data.
The data for retaining including the structure and formatting is
again extracted for use as the unit of side information for
decompressing data of similar media-type received in response to
future requests (step 430). Next, the unique identifier is computed
for the remaining data (step 432). The reduced data is used to
build the grammar and collect frequency counts for compression of
data (step 433) and the remaining data including the grammar and
frequency counts is compressed using YK compression without the use
of any side information (step 434). The compressed data including
the grammar and frequency counts is cached (step 435) by storing
the data in the device side information database 314 in association
with the unique identifier. Thus, the unit of side information is
reduced, by removing the displayable data, and stored at both the
mobile device 100 and the server.
[0120] Returning to step 408, the server searches the server side
information database 324 for the unit of side information
identified by the unique identifier of the unit of side information
provided in the request from the mobile device 100. Thus, the
server determines if the unit of side information is resident in
the server-side database 324 and, if so, the unit of side
information is retrieved along with the unique identifier, as shown
in FIG. 7 (step 436). After retrieving the unit side information
associated with the unique identifier of the side information, the
server builds the grammar and collects frequency counts and then
compresses the data (step 438). The server then transmits a
response to the mobile device 100. The compression method used is
identified in the response sent to the mobile device 100 along with
the identifier of the unit of side information and the requested
data is transmitted (step 440). In one example, an HTTP response
header is received. An exemplary HTTP response header can include,
for example:
[0121] HTTP/1.1 200 OK
[0122] Connection: keep-alive
[0123] Content-Encoding: side-info-impl
[0124] X-SideInfo-Identifier: 0x12345678
[0125] As described above, rather than waiting for all of the
requested data to be retrieved, the server can begin compressing
and streaming the response to the mobile device 100 shortly after
beginning retrieval of the requested data (when the requested data
begins to arrive). Again, there may be a minimum amount that the
server retrieves before compression and transmission. After
beginning transmission, the process returns to step 414 and, as
described above with reference to FIG. 6, the data for retaining is
determined. The process proceeds through the remaining steps 416 to
420 and the new unit of side information created from the data is
cached, storing the unit of side information in the server side
information database 324 in association with the unique identifier
for use in compressing data of the same media-type and data source
in response to future requests from the mobile device 100. Many
units of side information can therefore be stored in the server
side information database 324 and the side information cache size
can be managed using any suitable technique.
[0126] It will be appreciated that if the data sent to the mobile
device 100 at step 440 is identical to data previously sent to the
mobile device 100, the unit of side information cached at step 420
will be the same as a previously cached unit of side information
and will have the same side information identifier. Thus, only a
single cache entry is stored in the server side information
database 324 for the data as the unit of side information
overwrites the previous unit of side information stored in
association with the side information identifier. It will also be
appreciated that data such as an HTML page that differs in
displayable data from data previously sent to the mobile device 100
may result in identical side information and therefore an identical
side information identifier after reducing the data. Again, only a
single cache entry is stored in the server side information
database 324 in association with the side information
identifier.
[0127] The response including the unique identifier of the unit of
side information is received at the mobile device 100 (step 442)
and the decoder 103 loads the unit of side information for use in
decompressing the received data (step 444). The received data is
then decompressed using the unit of side information and rendered
on the display 110 (step 446). After all the data is received and
decompressed, the process returns to step 426 and, as described
above with reference to FIG. 6, the mobile device 100 identifies
the media-type and source of the requested data. The process
proceeds through the remaining steps 428 to 435 and the compressed
data including the grammar and frequency counts is cached, storing
the unit of side information including the grammar and frequency
counts in the device side information database 314 in association
with the unique identifier for use in decompressing data of the
same media-type and data source. Many units of side information can
therefore be stored in the device side information database 314 and
the side information cache size can be managed using any suitable
technique.
[0128] It will again be appreciated that if the data received at
the mobile device 100 at step 442 is identical to data previously
received at the mobile device 100, the unit of side information
cached at step 435 will be the same as a previously cached unit of
side information and will have the same side information
identifier. Thus, only a single cache entry is stored in the device
side information database 314 for the data as the unit of side
information overwrites the previous unit of side information stored
in association with the side information identifier. It will also
be appreciated that data such as an HTML page that differs in
content from data previously received at the mobile device 100 may
result in identical side information and therefore an identical
side information identifier after reducing the data. Again, only a
single cache entry is stored in the device side information
database 314 in association with the side information
identifier.
[0129] According to the present embodiment, the first time data of
a particular media-type and data source is requested, no side
information exists at the device side information database 314 and
therefore the request is sent without any unique identifier of a
unit of side information and it is determined at step 408 that no
side information is available. Thus, data retrieved is compressed
without the benefit of the use of side information. The second time
data of a particular media-type and data source is requested, the
server and the mobile device 100 have a unit of side information
stored in association with a unique identifier in their respective
side information databases 324, 314 and the unique identifier of
the unit of side information is included in the request from the
mobile device 100.
[0130] In the embodiments described above with reference to FIGS. 6
and 7, data is sent to the mobile device in response to receipt of
a request for data. It will be appreciated that data such as email
data can be sent to the mobile device 100 in a "push" operation,
and therefore, a unit of side information can be selected and the
data compressed and sent automatically without receipt of a request
for data transmission. Alternatively, the server can communicate
with the mobile device 100 that data is to be transmitted and await
a request including a unique identifier of a unit of side
information to be used in compression.
[0131] Rather than the data being reduced at both the mobile device
100 and the server, the server can, instead, reduce the data to
form the unit of side information and then send the unit of side
information to the mobile device 100. Further, the unique
identifier can be sent to the mobile device 100 for storage of the
unit of side information in association with the unique identifier
at the device side information database 314. Thus, after computing
the side information identifier at step 418, for example, the unit
of side information and the side information identifier can be sent
to the mobile device 100 for storage, thereby reducing the
calculations performed by the processor at the mobile device 100.
Alternatively, it is possible that the mobile device 100 can reduce
the side information and send the reduced side information to the
server for storage.
[0132] Reference is now made to FIGS. 8 and 9 to describe an
example of data reduced at the mobile device 100, in steps 428 and
430 as described with reference to FIG. 6, and at the server, in
steps 414 and 416. FIG. 8 shows a simplified example of data
retrieved by the server and received at the mobile device 100. As
shown in the present example, an HTML document includes CSS
descriptions 450 and JavaScript 452 contained therein. Constituents
of the data are determined to identify the displayable data and the
remaining data including structure and formatting information for
rendering data based on the media-type of the data (step 414). The
remaining data including the structure and formatting is then
extracted for use as the unit of side information for compressing
data of similar media-type and data source in response to future
requests (step 416). The remaining data, according to the present
example, is shown in FIG. 9. As shown, the reduced data in FIG. 9
includes the CSS descriptions 450 and JavaScript 452. The
displayable HTML data identified by the numeral 454 in FIG. 8,
"This is some content." and "This is some more content.", is not
included in the reduced data, however. Thus, in the present
example, the HTML displayable data is not included in the reduced
data while the remaining data is included.
[0133] Reference is now made to FIGS. 6, 7 and 10 to describe a
method of interactive compression including creating side
information in accordance with another embodiment. Many of the
steps in the present embodiment are similar to those described
above with reference to FIGS. 6 and 7 and therefore, these steps
are referred to but are not described in detail again.
[0134] A request for data is transmitted from the mobile device 100
to the server along with an indication that the mobile device 100
is YK-enabled (step 400). The mobile device 100 then awaits receipt
of the requested data transmitted from the server.
[0135] The request sent from the mobile device 100 is received at
the server (step 402) and the server identifies the requested data
and begins retrieving the requested data (step 404). The requested
data can be located within the server or can be accessible through
a remote server, such as HTTP server 275, over the network 200. The
server then determines the media-type as well as the data source
(step 406) and the server searches the server side information
database 324 to determine if a suitable unit of side information,
based on the media-type and data source, is associated with the
mobile device 100 (step 408). If no suitable unit of side
information has been previously stored for the mobile device 100
for the identified media-type and data source, the data is
compressed without the use of side information (step 410). Again,
the first time data of a particular media-type and data source is
requested, no side information exists in association with the
mobile device 100 and therefore the data retrieved is compressed
without the benefit of the use of side information.
[0136] The server then transmits a response to the mobile device
100. The compression method used is identified in the response sent
to the mobile device 100 (step 412) and the requested data is
transmitted. Again, the server can begin streaming the response to
the mobile device 100 shortly after beginning retrieval of the
requested data (when the requested data begins to arrive). It will
be appreciated that there may be a minimum amount that the server
retrieves before the side information is selected and before
starting to transmit the data. It is not necessary that all the
data be retrieved at the server prior to beginning compression and
transmission of data, however.
[0137] Data for retaining is then determined (step 414). In the
present embodiment, the determination of data for retaining
includes a number of sub-steps as shown in FIG. 10. First, the
constituents of the data and a hierarchical node tree structure are
determined (step 460). All structure and formatting as well as data
for rendering is determined based on the media-type of the data.
Next, the number of children or dependent nodes in the node tree
structure and the total length of text (the number of characters)
for each node is determined (step 462). In the present application,
child nodes include all those nodes that are directly dependent
from a node and all subsequent nodes in the path (further dependent
nodes). Similarly, parent nodes include the node from which a child
node depends and all further nodes in the path in which the child
node depends. A numerical ratio of child nodes to total length of
text for rendering is also determined for each node (step 464).
Next, the ratio determined for each node at step 464 is compared to
a predetermined value to determine if the ratio is greater than the
predetermined value, beginning with the root node of the tree
structure and then traversing across the tree structure. If any one
node has a ratio that exceeds the predetermined value, then it is
determined that the node along with all the child nodes are to be
retained (step 468). It is determined if there are further nodes in
the tree (step 470) and if not, the process proceeds to the next
step as shown in FIG. 6 (step 416). If there are further nodes in
the tree, however, the next highest node in the tree is determined
(step 471) and the process returns to step 466 where it is
determined if the ratio for the exceeds the predetermined
value.
[0138] If at step 466 it is determined that the ratio does not
exceed the predetermined value, it is then determined if the ratio
is equal to zero (step 472). If the ratio is not equal to zero, it
is determined that the node is to be retained (step 478), the next
node that is a child node of the current node is determined (step
480) and the process returns to step 466 where it is determined if
the ratio for the child node, determined at step 480, is greater
than the predetermined value. If not, the process proceeds to step
472.
[0139] If, at step 472, it is determined that the ratio is equal to
zero, it is then determined if the node is a node of text data for
rendering (step 474). If not, it is determined that the node is to
be retained (step 476) and the process proceeds to step 470. If it
is determined that the node is a node of text data for rendering,
the process proceeds directly to step 470. As described, it is
determined if there are further nodes in the tree (step 470) and if
not, the process proceeds to the next step as shown in FIG. 6 (step
416). If there are further nodes in the tree, however, the next
highest node in the tree is determined (step 471) and the process
returns to step 466 where it is determined if the ratio for the
next node exceeds the predetermined value.
[0140] The data identified in the sub-steps of step 414 to be data
for retaining is then extracted for use as the unit of side
information for compressing data of similar media-type and data
source in response to future requests (step 416). The unique
identifier is computed for the extracted data, referred to now as
the unit of side information (step 418) and the unit of side
information is cached (step 420), storing the unit of side
information in the server side information database 324 in
association with the unique identifier for use in compressing data
of the same media-type and data source in response to future
requests from the mobile device 100. Again, the server side
information database 314 can store more than one unit of side
information as units of side information apply to like data formats
and data sources.
[0141] The response including the identity of the compression
method used is received at the mobile device 100 (step 422) and it
is determined that no side information was used to compress the
data. Thus, the decoder 103 decompresses the received data and
renders the data on the display 110 (step 424). The mobile device
100 determines the media-type of the requested data (step 426) and
the data for retaining is determined based on the media-type of the
data (step 428). In the present embodiment, the determination of
data for retaining includes a number of sub-steps that are
identical to those described above with reference to step 414 and
to FIG. 10. It will be appreciated that when it is determined that
there are no further nodes at step 470, the process proceeds to
step 430 where the data identified at step 428 to be data for
retaining is then extracted for use as the unit of side information
for compressing data of similar media-type and data source (step
430). The unique identifier is computed for the extracted data,
referred to now as the unit of side information (step 432). The
extracted data is used to build the grammar and collect frequency
counts for compression of data (step 433) and the extracted data
including the grammar and frequency counts is compressed using YK
compression without the use of any side information (step 434). The
compressed data including the grammar and frequency counts is
cached (step 435), storing the compressed data in the device side
information database 314 in association with the unique identifier
for use in decompressing data of similar media-type received in
response to future requests. Again, the device side information
database 314 can store more than one unit of side information as
units of side information apply to like data formats.
[0142] Returning to step 408, the server searches the server side
information database 324 to determine if a suitable unit of side
information, based on media-type and data source, is associated
with the mobile device 100. The server thereby determines if a
suitable unit of side information has been previously stored for
the mobile device 100 for the media-type and the data source and if
so, the unit of side information is retrieved along with the unique
identifier, as shown in FIG. 7 (step 436). According to the present
embodiment, the first time data of a particular media-type and data
source is requested, no side information exists in association with
the mobile device 100 and therefore the data retrieved is
compressed without the benefit of the use of side information. The
second time data of a particular media-type and data source is
requested, the server and the mobile device 100 have a unit of side
information stored in association with a unique identifier in their
respective side information databases 324, 314.
[0143] After retrieving the unit of side information based on the
media-type and data source, along with the unique identifier of the
side information, the server builds the grammar and collects
frequency counts and then compresses the data (step 438). The
server then transmits a response to the mobile device 100. The
compression method used is identified in the response sent to the
mobile device 100 along with the identifier of the unit of side
information and the requested data is transmitted (step 440). As
described above, rather than waiting for all of the requested data
to be retrieved, the server can begin streaming the response to the
mobile device 100 shortly after beginning retrieval of the
requested data (when the requested data begins to arrive). After
beginning transmission of the identifier of the unit of side
information and the requested data, the process returns to step 414
and, as described above with reference to FIG. 6 and to FIG. 10,
the data for retaining is determined (step 416). The process
proceeds through the remaining steps 416 to 420 and the new unit of
side information created from the data is cached, storing the unit
of side information in the server side information database 324 in
association with the unique identifier for use in compressing data
of the same media-type and data source in response to future
requests from the mobile device 100. Many units of side information
can therefore be stored in the server side information database 324
and the side information cache size can be managed using any
suitable technique. If the data sent to the mobile device 100 at
step 440 is identical to data previously sent to the mobile device
100, the unit of side information cached at step 420 will be the
same as a previously cached unit of side information and will have
the same side information identifier. Further, if the data differs
only in displayable text that is not retained for use as side
information, the unit of side information will be the same as a
previously cached unit of side information. Thus, only a single
cache entry is stored in the server side information database 324
for the data as the unit of side information overwrites the
previous unit of side information stored in association with the
side information identifier.
[0144] The response including the unique identifier of the unit of
side information is received at the mobile device 100 (step 442)
and the unit of side information resident on the mobile device 100,
in the side information database 314, is identified using the
unique identifier. The decoder 103 loads the unit of side
information for use in decompressing the received data (step 444)
and the received data is then decompressed using the unit of side
information and rendered on the display 110 (step 446).
[0145] After all the data is received and decompressed, the process
returns to step 426 of FIG. 6. The process proceeds through the
steps 426 to 435, as described above, and the new unit of side
information created from the data including the grammar and
frequency counts is compressed and cached, storing the unit of side
information in the device side information database 314 in
association with the unique identifier for use in decompressing
data of the same media-type and data source. Again, many units of
side information can therefore be stored in the device side
information database 314 and the side information cache size can be
managed using any suitable technique.
[0146] Reference is now made to FIGS. 11 to 15 with continued
reference to FIGS. 6, 7 and 10 to describe an example of
interactive compression including creating side information in
accordance with the present embodiment. FIGS. 11A and 11B show one
example of data requested by the mobile device 100 in the request
for data transmitted at step 400. The data shown in FIG. 11B is a
continuation of data from FIG. 11A and is shown on a second page as
a result of the length of the combined data only.
[0147] The request for data is received at the server along with
the indication that the mobile device 100 is YK-enabled (step 402)
and the server begins retrieving the requested data (step 404). The
server then determines the media-type as well as the data source
(step 406) and the server searches the server side information
database 324 to determine if a suitable unit of side information,
based on the media-type and data source, is associated with the
mobile device 100 (step 408). In the present example, no suitable
unit of side information has been previously stored for the mobile
device 100 for the identified media-type and data source, the data
is compressed without the use of side information (step 410).
[0148] The server then transmits a response to the mobile device
100. The compression method used is identified in the response sent
to the mobile device 100 (step 412) and the requested data is
transmitted. Again, the server can begin streaming the response to
the mobile device 100 shortly after beginning retrieval of the
requested data (when the requested data begins to arrive).
[0149] Data for retaining is then determined (step 414). First, the
constituents of the data and a hierarchical node tree structure are
determined (step 460). In the present example, the data shown in
FIGS. 11A and 11B can be represented in the node tree shown in FIG.
12 including the root node 500 representing the data format (HTML)
and nodes 502 to 530 that represent all structure and formatting as
well as text data for rendering. Thus, all structure and formatting
as well as data for rendering is determined based on the data
format. Next, the number of children or dependent nodes and the
total length of text for rendering (the number of characters) for
each node is determined (step 462). A numerical ratio of child
nodes to total length of text is determined for each node (step
464). The ratios for each node are represented in node tree shown
in FIG. 13. The node tree of FIG. 13 is identical to that of FIG.
12, with ratios inserted for the purpose of the present
description. As shown, the root node, 500 includes 15 child nodes
and a total length of text for rendering of 1465 characters. The
node 502 includes 1 child node and 0 text for rendering. It will be
appreciated that the nodes 514, 520, and 530 represent the text for
rendering 540, 542 and 544, respectively, shown in FIGS. 11A and
11B. The remainder of the nodes in the tree represent non-text
nodes.
[0150] Next, the ratio determined for each node at step 464 is then
compared to a predetermined value to determine if the ratio is
greater than the predetermined value, beginning with the root node
of the tree structure. The predetermined value can be any suitable
value. In the present example, the predetermined value is 0.1. The
root node has a ratio of 15:1465, which is equal to 0.01. This
number is not greater than the predetermined value. The ratio does
not equal zero, however (step 472). Thus, the node is identified as
a node for retaining (step 478) and the process proceeds to the
next child node (step 480). The next child node is the node 502
which has a ratio of 1:0, which is an infinite number. Thus, the
node 502 and all child nodes (node 504) are identified as nodes for
retaining (step 468). There are further nodes (step 470) and
therefore, the process proceeds to the next highest node (step
471), which in the present example is the node 506 representing the
"BODY". The node 506 has a ratio of 12:1465, which is equal to
0.008. This ratio does not exceed 0.1 (step 466) and the ratio is
not equal to zero (step 478). Thus, the node is identified as a
node for retaining (step 478) and the process proceeds to the next
child node (step 480) which, in the present example, is the node
508. The node 508 has a ratio of 6:10 that equals 0.6. This value
exceeds the predetermined value of 0.1 (step 466) and therefore
this node along with all child nodes 510, 512, 514, 516, 518, and
520 are identified as nodes for retaining (step 468). There are
further nodes (step 470) and therefore, the process proceeds to the
next highest node (step 471). The node 522 has a ratio of 1:0,
which is an infinite number. Thus, the node 522 and all child nodes
(node 524) are identified as nodes for retaining (step 468). There
are further nodes (step 470) and therefore, the process proceeds to
the next highest node (step 471), which in the present example is
the node 526. The node 526 has a ratio of 2:1455, which is equal to
0.001. This number is not greater than the predetermined value
(step 466). The ratio does not equal zero, however (step 472).
Thus, the node is identified as a node for retaining (step 478) and
the process proceeds to the next child node (step 480). The node
528 has a ratio of 1:1455, which is less than 0.001. This number is
not greater than the predetermined value (step 466). The ratio does
not equal zero, however (step 472). Thus, the node is identified as
a node for retaining (step 478) and the process proceeds to the
next child node (step 480). Finally, the node 530 has a ration of
0:1455, which is equal to 0. This number is not greater than the
predetermined value (step 466) and is determined to be equal to
zero (step 472). The node is determined to be text data for
rendering at step 474 and therefore the process proceeds to step
470. At step 470 it is determined that there are no further nodes
in the node tree and the process continues at step 416.
[0151] The data identified at step 414 to be data for retaining is
then extracted for use as the unit of side information for
compressing data of similar media-type and data source in response
to future requests (step 416). The extracted data for use as the
unit of side information is represented in the tree structure shown
in FIG. 14 and is shown in FIG. 15. It will be appreciated that in
the present embodiment, all data was retained for use as the unit
of side information with the exception of the text data represented
by the number 530 and corresponding the text 544 in FIG. 11B. The
unique identifier is computed for the extracted data, referred to
now as the unit of side information (step 418) and the unit of side
information is cached (step 420), storing the unit of side
information in the server side information database 324 in
association with the unique identifier for use in compressing data
of the same media-type and data source in response to future
requests from the mobile device 100. [00113] The response including
the identity of the compression method used is received at the
mobile device 100 (step 422) and it is determined that no side
information was used to compress the data. Thus, the decoder 103
decompresses the received data and renders the data on the display
110 (step 424). The mobile device 100 determines the media-type of
the requested data (step 426) and the data for retaining is
determined based on the media-type of the data (step 428). In the
present embodiment, the determination of data for retaining
includes a number of sub-steps that are identical to those
described above with reference to step 414 and to FIGS. 10 to 15.
It will be appreciated that when it is determined that there are no
further nodes at step 470, the process proceeds to step 430 where
the data identified at step 428 to be data for retaining is then
extracted for use as the unit of side information for compressing
data of similar media-type and data source (step 430). The unique
identifier is computed for the extracted data (step 432). The
extracted data is used to build the grammar and collect frequency
counts for compression of data (step 433) and the extracted data
including the grammar and frequency counts is compressed using YK
compression without the use of any side information (step 434). The
compressed data including the grammar and frequency counts is
cached (step 435), storing the compressed data in the device side
information database 314 in association with the unique identifier
for use in decompressing data of similar media-type received in
response to future requests. Again, the device side information
database 314 can store more than one unit of side information as
units of side information only apply to like data formats.
[0152] It will be appreciated that if the server determined at step
408 that a suitable unit of side information, based on the
media-type and data source, is associated with the mobile device,
the data transmitted to the mobile device would have been
compressed at the server side using the suitable unit of side
information and decompressed at the mobile device 100 using the
corresponding unit of side information, as shown in FIG. 7.
[0153] In the embodiment and the example described above with
reference to FIG. 6, 7 and 10, data is sent to the mobile device in
response to receipt of a request for data. It will be appreciated
that data such as email data can be sent to the mobile device 100
in a "push" operation, and therefore, a unit of side information is
selected and the data is compressed and sent automatically without
receipt of a request for data at the server. Thus, a request for
data is not sent from the mobile device 100 as described.
[0154] It will be appreciated that, in the embodiment described
above with reference to FIG. 10, some text for rendering is
retained. In the example described above, the text nodes 514 and
520 are retained. Thus, the corresponding text 540, 542
respectively is retained in the unit of side information. This is
particularly advantageous as the text nodes that are retained are
likely to be shared between data from the same source. In the above
HTML example, the nodes 514 and 520 are likely to be shared with
HTML documents from the same source, for example from the same
domain, and therefore the inclusion of this text data in the side
information improves compression using this side information. In a
particular example, a news Web site may contain a Web page that
includes text in articles as well as links to other pages within
the site such as "World", "Sports" and "Finance". While the text in
the articles is likely to vary, the text in the links is likely to
be the same as that of other Web pages within the site. The
inclusion of this text further improves compression.
[0155] In the embodiments described above with reference to FIGS. 6
and 7, the grammar is built and statistics compiled and the side
information is compressed at the mobile device 100 prior to storing
in the device side information database 314. It will be appreciated
that, instead, the grammar can be built and statistics compiled "on
the fly" rather than prior storing the side information in the
device side information database 314. Further, the side information
can be stored without compression. It will also be appreciated that
the grammar can be built and statistics compiled prior to storing
the side information in the server side information database 324
rather than building grammar and compiling statistics after
retrieving the side information from the database during a
compression operation.
[0156] In the present application, application-layer data
compression is performed for compressing, for example, Web page
content or email content. Data transmitted in a mobile
device/server system in which a server asynchronously transmits
data to one or more mobile devices or in which a mobile device
requests data from one or more servers can be compressed using a
compression method employing side information such as Yang-Kieffer
(YK) compression. The side information is implemented as a
shared-state between the data compressor (encoder) and the data
decompressor (decoder). The use of side information in such a
compression method can provide marked improvements in data
compression rates, resulting in network bandwidth savings when the
data is transmitted.
[0157] Reducing the side information can result in a significant
reduction in the size of the unit of side information while
preserving the portions of the document most likely to be common
across other documents of the same media-type and originating from
the same source. The reduction in size of the unit of side
information results in a significant reduction in RAM used in the
RAM constrained mobile device during decompression of data at the
decoder. It will be appreciated that, for example, many pages
within a website may have very similar layout and formatting and,
as a result, share many blocks of HTML, CSS-style descriptions, and
JavaScript code. The most significant differences may be in
displayable data of the pages. By removing at least some of the
displayable data in the side information used for compression and
decompression, significant reductions in RAM used can be realized
while still benefiting from improved compression as a result of the
use of the reduced side information.
[0158] According to one aspect, there is provided a
computer-implemented method of creating side information from data
for use in interactive compression. The method includes identifying
constituents of the data, extracting at least one of the
constituents, and retaining the extracted constituents for use as a
unit of side information.
[0159] According to another aspect, there is provided a mobile
device including a housing, a display device exposed by the
housing, an input device, a memory unit within the housing, and a
processor within the housing and operably connected to the display
device, the input device and the memory unit for executing a
program stored in the memory unit to cause the electronic device to
create side information from data for use in interactive
compression. The side information is created by identifying
constituents of the data, extracting at least one of the
constituents, and retaining the extracted constituents for use as a
unit of side information.
[0160] According to yet another aspect, there is provided a
computer program product including a computer-readable medium
having computer-readable code embodied therein for execution by a
processor of a mobile device for creating side information from
data for use in interactive compression by identifying constituents
of the data, extracting at least one of the constituents, and
retaining the extracted constituents for use as a unit of side
information.
[0161] Embodiments of the disclosure may be represented as a
software product stored in a machine-readable medium (also referred
to as a computer-readable medium, a processor-readable medium, or a
computer usable medium having a computer readable program code
embodied therein). The machine-readable medium may be any suitable
tangible medium, including magnetic, optical, or electrical storage
medium including a diskette, compact disk read only memory
(CD-ROM), memory device (volatile or non-volatile), or similar
storage mechanism. The machine-readable medium may contain various
sets of instructions, code sequences, configuration information, or
other data, which, when executed, cause a processor to perform
steps in a method according to an embodiment of the disclosure.
Those of ordinary skill in the art will appreciate that other
instructions and operations necessary to implement the described
embodiments may also be stored on the machine-readable medium.
Software running from the machine-readable medium may interface
with circuitry to perform the described tasks.
[0162] The above-described embodiments of the present disclosure
are intended to be examples only. Alterations, modifications and
variations may be effected to the particular embodiments by those
of skill in the art without departing from the scope which is
defined solely by the claims appended hereto.
* * * * *
References